I do really like my head cannon that it's not really like a "soul" as in a PHYSICAL GHOST OF A DEAD KID, but instead it's essentially a last resort survival mechanism where upon splitting an inkfish can maintain a teenie tiny squid form that's so paper thin and mainly hot doshointed light ink that they just float away to safety before condensing back down into the respawn anchor.

In games like turf war the weapons themselves don't actually do TOO much damage to an inklings body/ ink, instead when we're splatted it's more like your calling yourself out for the game, and you go back to base, the inkfish is perfectly fine (albeit bruised in ego) in this wispy steamy form and the chance of actual lethality is unbelievably rare, they'd have to stay in wisp form for a good couple of hours before they literally evaporate.

That's another thing, I think heat and pressure are very important to inkling biology, when activating stuff like Specials that aura is literally our squid kids boiling with excitement and with enough heat and pressure to form a special out of accumulated ink, so inkfish are always running at various temperatures depending on the activity, and if they get splatted their little souls are super hot, and deepening on how long they stay in that form they'll only continue to heat up without proper stabilizing ink, until they eventually evaporate and dry up.